Water dispersible nonwoven fabric

ABSTRACT

A water dispersible nonwoven fabric comprising one or more layers of overlapping, intersecting fibers and from about four percent to about thirty-five percent by weight of an alkali cellulose ether sulfate resin binder, said nonwoven fabric having good tensile strength and abrasion resistance in the presence of body fluids such as urine, blood, and menstrual fluid. The nonwoven fabrics may be incorporated in body fluid absorbent products such as sanitary napkins, diapers, surgical dressings, and the like.

United States Patent Tune Apr. 16, 1974 [54] WATER DISPERSIBLE NONWOVEN3,554,788 1/1971 Fechillas 117/140 FABRIC 3,580,253 5/1971 Bernardin128/290 W 3,521,638 7/1970 Parrish 128/284 Inventor: Deger Tune, Edison,NJ.

Johnson & Johnson, New Brunswick, NJ.

Assignee:

US. Cl 128/284, 117/143 A, 128/287, 128/290 W, 161/169, 260/224 Int. Cl.A4lb 13/02, A61f 13/16 Field of Search 128/156, 284, 286, 287, 128/290,296; 117/140, 143 A; 161/151,

References Cited UNITED STATES PATENTS 11/1969 Constanza et a1. .L128/284 Primary Examiner-Charles F. Rosenbaum [5 7] ABSTRACT A waterdispersible nonwoven fabric comprising one or more layers ofoverlapping, intersecting fibers and from about four percent to aboutthirty-five percent by weight of an alkali cellulose ether sulfate resinbinder, said nonwoven fabric having good tensile strength and abrasionresistance in the presence of body fluids such as urine, blood, andmenstrual fluid. The nonwoven fabrics may be incorporated in body fluidabsorbent products such as sanitary napkins, diapers, surgicaldressings, and the like.

25 Claims, 5 Drawing Figures 1 WATER DISPERSIBLE NONWOVEN FABRIC Thisinvention relates to new nonwoven fabrics which are readily dispersiblein water and are flushable. More particularly, this invention relates tononwoven fabrics which, in addition to having the abovementioneddesirable characteristics, exhibit satisfactory tensile strength whenthey are contacted with body fluids.

Nonwoven fabrics are widely used as components of such disposable goodsas sanitary napkins, diapers, bandages, and the like. Such fabrics, ifthey are to function effectively, must maintain their structuralintegrity, as well as exhibit satisfactory tensile strength, when theyare wet or damp with the various body fluids, for example, blood,menstrual fluid and'urine, with which they come into contact during use.It has been recognized that if such nonwoven fabrics, while retainingtheir strength in body fluids, were to lose substantially all theirtensile strength when exposed to water and become readily dispersibletherein, disposal problems would be substantially eliminated since thefabrics could be easily and conveniently flushed away in a water closet.

Unfortunately, in an attempt to provide nonwoven fabrics having certainin-use characteristics, prior methods have rendered the fabricnondispersible in water. For example, nonwovens have been bonded withbody fluid-insoluble resins which impart in-use strength. Generally,however, such resins have also been water insoluble as well and haveimpeded flushing of the fabric. Therefore, less desirable methods ofdisposal such as incineration or dumping must be employed.

SUMMARY OF INVENTION l have now discovered a bonded nonwoven fabricwhich, in addition to having good strength when dry, and satisfactorystrength and abrasion resistance in the presence of most body fluids,such as urine, blood, menstrual fluid and the like, is easilydispersible in water and hence is flushable in home water closets andcapable of disposal in standard sewer systems or septic systems. ln thisconnection when an article, for example, a barrier means, an absorbentcore, a nonwoven fabric or the like is referred to herein as beingflushable, it is meant that that article may be deposited in, andflushed through, a water closet without any undue clogging of the watercloset or its auxiliary piping. When such an article is referred toherein as being water dispersible. it is meant that that article, whenplaced in water, loses its integrity and is flushable.

The improved nonwoven fabric of this invention comprises one or morelayers of overlapping, intersecting fibers and from about four percentto about 35 percent by weight of the fabric of binder. The bindercomprises an alkali cellulose ether sulfate resin, such as, for example,an alkali alkyl cellulose sulfate, an alkali hydroxyalkyl cellulosesulfate or an alkali hydroxyalkyl alkyl cellulose sulfate wherein eachof the alkyl and hydroxyalkyl groups contains not more than four carbonatoms.

Examples of the alkali cellulose ether sulfates which may be used asbinders for the nonwoven fabrics herein described are such alkali alkylcellulose sulfates as sodium methylcellulose sulfate, potassium ethylcellulose sulfate, sodium propyl cellulose sulfate and potassium butylcellulose sulfate; such alkali hydroxyalkyl cellulose sulfates as sodiumhydroxyethyl cellulose sulfate, sodium hydroxypropyl cellulose sulfateand sodium hydroxybutyl cellulose sulfate; and such alkali hydroxyalkylalkyl cellulose sulfates as sodium hydroxypropyl methyl cellulosesulfate, potassium hydroxyethyl ethyl cellulose sulfate and sodiumhydroxyethyl propyl cellulose sulfate.

The fabrics prepared in accordance with this invention have good drytensile strength depending upon, among other things, the amount ofbinder applied to the fabric and the manner in which it is applied. Theyare abrasion resistant and retain a significant part of their drytensile strength in solutions containing about 0.8 percent or more byweight of sodium chloride, and yet are readily dispersible in water.Because of this latter property, the nonwoven fabrics of this inventionare uniquely suited for use in products to be contacted with such bodyfluids as blood, menstrual fluid, urine and the like. These fluids, ingeneral, exhibit properties which, with respect to the binder, areanalogous to aqueous salt solutions having a salt content which variesfrom about 0.8 to about 1.5 percent by weight of sodium chloride. On theotherhand tap water normally supplied to water closets and the likegenerally has an extremely low concentration of salt, for example, lessthan 250 parts per million of chloride ion. It has been discovered thatthe nonwoven fabrics made as described herein maintain their integrityfor a substantial period of time in solutions having a saltconcentration exhibiting the properties of body fluids whereas theydisplay a far lower resistance to dispersion in tap water. This uniqueproperty is a function of the degree of sulfate substitution(hereinafter, D.S.) which expresses the average number of sulfate groupsper anhydroglucose unit of the cellulosic ether. The nonwoven fabricbonded by the aforementioned cellulosic resins will exhibit increasingdispersibility in water and decreasing strength in salt solutions as theD8. of the cellulosic resin is increased. It has been discovered that anonwoven fabric bonded by resins having a D8. varying from about 0.10 toabout 0.30 is useful in products designed to be contacted by variousbody fluids. In another aspect of this invention, the nonwoven fabricsare incorporated into such body fluid absorbent products as sanitarynapkins, diapers, surgical dressings and the like. These productsgenerally include an absorbent core, comprising one or more layers of anabsorbent fibrous material. The core may also comprise one or morelayers of a fluid-pervious element, such as tissue, gauze, plasticnetting, etc. These are generally useful as wrapping materials to holdthe components of the core together. Additionally, the core may comprisea fluidimpervious element or barrier means to preclude the passage offluid through the core and on to its outer surfaces. In accordance withthis aspect of the instant invention, a body fluid absorbent product isprovided having a nonwoven fabric in contact with an absorbent core, thenonwoven fabric comprising a layer of overlapping intersecting fibersfrom about 4 to about 35 percent by weight of fabric of an alkalicellulose ether sulfate resin binder having an average of from about0.10 to about 0.30 sulfate groups per anhydroglucose unit.

The invention will be more clearly understood by reference to theattached drawings taken together with the following description.

BRIEF DESCRIPTION'OF THE DRAWINGS FIG. 1 is a plan view of a bondednonwoven fabric in accordance with the present invention;

FIG. 2 is a perspective view of a sanitary napkin embodying thisinvention with parts broken away to show the interior constructionthereof;

FIG. 3 is a cross-sectional view taken approximately along lines 3-3 ofFIG. 2;

FIG. 4 is a perspective view of a disposable diaper embodying thisinvention with parts broken away to show the interior constructionthereof; and

FIG. 5 is a cross-sectional view taken approximately along lines 5-5 ofFIG. 4.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, thereis showna water dispersible nonwoven fabric 10. The fabric comprises alayer of overlapping, intersecting fibers 11 having substantiallyuniformly distributed therein an alkali cellulose ether sulfate binder12 as hereinafter described.

The alkali cellulose ether sulfates used as the binder for the nonwovenfabrics of this invention may be produced by first forming the etherderivatives of cellulose and then sulfating with a suitable sulfatingagent. The ether derivatives are generally prepared by reacting apurified form of cellulose with either an alkyl halide, and alkyleneoxide or both to form either the alkyl ether, the hydroxyalkyl ether orthe hydroxyalkylalkyl ether, respectively. Unsulfated cellulose ethersare presently available as, for example, the methylcellulose andhydroxypropyl methylcellulose ethers sold under the trandemark METHOCELand the ethylcellulose ethers sold under the trademark ETHOCEL, allavailable from the Dow Chemical Company, Inc. of Midland, Michigan.Hydroxyethyl cellulose ethers are available from Hercules, Incorporated,and Union Carbide Corporation under the trademarks NATROSOL andCELLOSIZE, respectively.

Table A below illustrates properties of typical ethers suitable forsulfating and use in accordance with this invention:

Methyl cellulose 50-60000 cps l9-33% by weight methyl 4-12'71 by weightpropylene glycol ether 5% ethyl cellulose in 80/20 (wt./wt.)Toluene/Ethanol at 25C.

2% (wt.) Aqueous Solution at C.

The average degree of substitution of alkyl groups per anhydroglucoseunit.

The ethers may be sulfated in accordance with a process described in U.S. Patent application Ser. No. 232,371, filed Mar. 7, 1972 whereby analkali sulfating agent is prepared by reacting acetic anhydride withsulfuric acid and an alkali sulfate, all in an acetic acid solution, toform alkali acetyl sulfate. The alkali acetyl sulfate is then reactedwith the cellulose ether to yield the alkali cellulose ether sulfateresin.

In accordance with this invention, it has been discovered that bymodifying the D.S. of the cellulosic resin binder, the salt resistanceand water dispersibility of the bonded nonwoven fabric can be modifiedto provide fabrics which will function effectively when contacted byvarious body fluids and which may beflushed away in a water closet.Specifically, by lowering the degree of sulfation of the cellulosicresins, the fabrics of this invention become more resistant to saltsolutions in that they retain their integrity after being subjected tothese solutions for long periods of time andin that they exhibit highertensile strengths when subjected to a given salt concentration for agiven period of time. In general, if the D.S. of the cellulosic resin ismaintained at below about 0.3, an adequately salt resistant nonwovenfabric results. Preferably, the D. S. should be maintained at belowabout 0.25. While the resistance of the nonwoven fabrics to saltsolutions having a salt concentration exhibiting the properties of bodyfluids increases greatly with decreasing D.S., the ability of thefabrics to disperse readily in water is maintained until extremely lowD.S. values are reached. Adequate water dispersibility is achieved whenthe D.S. of the cellulosic resin is maintained at a value of at leastabout 0.10. Preferably, the D. S. should be not less than about 0. l 5.

The aforementioned alkali cellulose ether sulfate resins are used tobond a base layer of fibers to provide the nonwoven fabric of thisinvention. Suitable base layers comprise most of the well-known fibers,the choice depending upon, for example, fiber cost and the intended enduse of the finished fabric. For instance, the base layer may includenatural fibers such as cotton, linen, jute, hemp, cotton linters, wool,wood pulp, etc. Similarly, regenerated cellulosic fibers such as viscoserayon and cuprammonium rayon, modified cellulosic fibers, such ascellulose acetate, or synthetic fibers such as those derived frompolyvinyl alcohol, polyesters, polyamides, polyacrylics, etc., alone orin combination with one another, may likewise be used. Natural fibersmay be blended with regenerated, modified, and- /or synthetic fibers ifso desired.

The length of the fiber is important in producing the fabrics of thepresent invention. The minimum length of the fibers depends on themethod selected for forming the base layer. For example, where the baselayer is formed by carding, the length of the fiber should usually be aminimum of V2 inch in order to insure uniformity. Where the base layeris formed by air deposition or water deposition techniques, the minimumfiber length may be about 0.05 inch. It has been found that when asubstantial quantity of fibers having a length greater than about 2inches is placed in the fabric, though the fibers will disperse andseparate in water, their length tends to form ropes of fibers which areundesirable when flushing in home water closets. It is preferred thatthe fiber length be 1% inches or less so that the fibers will not rope"when they are flushed through a toilet.

The base layers suitable for conversion into the fabric of the presentinvention may be formed by carding, garnetting, air deposition, waterdeposition, or any of the other various techniques known in the art, Thefibers in the. layer may be oriented predominantly in one direction asin a card web or a card web laminate or they may be randomly oriented asin a layer formed by air deposition techniques. For sanitary napkincoverings, disposable diaper facings and similar uses where the fabricis to be flushable, the web is fairly thin and should weigh between to400 grains per square yard. Where the fabric must possess a substantialamount of strength, uniform fiber distribution is important so as toavoid weak spots in the final nonwoven fabric. Uniform base layers maybe produced by carding in which case it is advantageous to use fiberswhich have good carding characteristics and can be blended into auniform carded web with facility. Fibers of viscose rayon and cotton areboth satisfactory in this respect.

The amount of alkali cellulose ether sulfate binder distributed in thebase layer should be from about 4 to 35 percent by weight of the finalnonwoven fabric. If less than about 4 percent of the cellulosic binderis employed, the fabric does not have sufficient strength and abrasionresistance to be of any utility. If more than about 35 percent of thecellulosic binder is employed, the fabric may lose desirable propertiessuch as absorbency and softness.

It is preferred that the amount of alkali cellulose ether sulfate binderbe between about 4 to percent by weight of the final nonwoven fabric inorder to ensure optimum water dispersibility.

The binder may be distributed in the base layer by printing, spraying,impregnating or by any other technique wherein the amount of binder maybe metered and the binder can be distributed uniformly within the baselayer. The binder may be distributed throughout the entire base layer orit may be distributed therein in a multiplicity of small closely spacedareas. The binder may be distributed in lines running across, or at anangle to, the width of the web or in separate small shaped areas havingcircular, angular, square, or triangular configurations. It is preferredthat when the binder is applied to the fibrous layer there be leftunbonded areas in the layer. These unbonded areas of fibers readilyabsorb water which attacks the binder areas and makes the fabricdispersible in shorter periods of time.

For ease of application to the base fibrous layer, the cellulosic resinbinder may be dissolved in water, methanol, ethanol,-or in suitablemixtures thereof, to provide solutions containing up to about percent byweight of binder solids. Plasticizers, such as glycerol, polyethyleneglycol, and castor oil, may be added to the solution of the cellulosicresin, the amount of such plasticizers varying according to the softnessrequired in the final fabric. Perfumes, coloring agents, antifoams,bactericides, surface active agents, thickening agents and similaradditives may be incorporated into the solution of the cellulosic resinbinder if so desired. Other binding agents such aspolyvinyl alcohol oraqueous dispersions of, for example, polyvinyl chloride, polyvinylacetate, polyacrylates, polymethacrylates, copolymers of acrylates andmethacrylates, copolymers of vinyl acetate with acrylates and/ormethacryl'ates and copolymers of acrylates and/or methacrylates withvinyl chloride may be addedto the cellulosic binder solution in order toobtain fabrics having various desired properties.

Referring now to FIGS. 2 and 3 of the drawing, illustrated therein is anembodiment of the water dispersible non-woven fabricof this invention asused with a sanitary napkin 20.

Napkin 20 comprises an-absorbent core which is contacted by afluid-pervious cover 26 comprising the. bonded nonwoven fabric of thisinvention. The absorbent core comprises a pad 22 of absorbent fibrousma-' terial such as comminuted wood pulp fibers, cotton linters, rayonfibers, cotton staple, bleached sulfite linters, other cellulosic ormodified cellulosic fibers and the like. The absorbent core furthercomprises a fluidimpervious element or barrier means 24 which, forexample, may be a thin polyethylene sheet or any other suitablematerial. As best seen in FIG. 3, barrier means 24 overlies the sidesand the bottom surface of absorbent pad 22 (the bottom surface beingthat portion worn away from the body). Fluid-pervious cover 26 surroundsabsorbent pad 22 and barrier means 24 with the lateral edges thereofoverlapped and secured on the bottom surface of napkin 20. Cover 26 isextended beyond the ends of the absorbent core'to form the usualattachment tabs 28. While FIGS. 2 and 3 illustrate a tabbed napkin, itwill be understood by one skilled in the art that the advantagesaccruing to the use of the nonwoven fabrics of this invention areequally applicable to a tabless product, e.g., one where tabs are notused as attachment means and other attachment means such as, forexample, adhesive means, are used. It will also be understood that theabsorbent core may comprise, in addition to the absorbent pad andbarrier means, a fluid-pervious element such as gauze, tissue, plasticnetting and the like if increased strength and/or dimensional stabilityare desired. It will be further understood that the fluid pervious coverof this invention need not completely surround the absorbent pad asillustrated in FIGS. 2 and 3. For example one could provide a fluidpervious cover, the edges of which are adhered to the edges of thebarrier means; in such a case, the barrier means and fluid perviouscover would cooperate to form an enclosure for the pad of absorbentfibrous material.

The nonwoven fabric of this invention is uniquely suited to serve as afluid-pervious covering in a sanitary napkin; such as shown in FIGS. 2and 3', because is is resistant to abrasion and exhibits satisfactorytensile strength when it has been dampened or wetted with menstrualfluid, which has a salt content of about 0.8 to about 1.5 percent byweight. The fabics of this invention are resistant to solutionscontaining more than about 0.8 percent salt, and notwithstanding suchsalt resistance, the fabrics are completely dispersible when introducedinto water or into salt solutions whose salt content is less than about0.8 percent by weight. It will be apparent that, by employing awater-dispersible material for the barrier means and a water-dispersibleabsorbent pad, the sanitary napkin of FIGS. 2 and 3 may be convenientlyand completely disposed of by flushing through a water closet.

Alternatively, the illustrated napkin may be provided with a non-waterdispersible barrier means and a waterdispersible absorbent pad. In thatcase, fluid-pervious covering 26 is first removed and the barrier meansis separated from the pad; the pad and covering can then be dropped intoa water closet for disposal. In either case, the unique nonwoven fabricof this invention will be completely dispersed in a water closet underthe swirling action of the water supplied thereto and will not impairthe normal operation of the water closet and associated plumbing.Referring to FIGS. 4 and 5 of the drawing, there is illustrated thereinanother embodiment of the water dispersible nonwoven fabric of thisinvention as used with a disposable diaper 30.

Diaper 30'comprises an absorbent core and a fluidpervious facing 36comprising the nonwoven fabric of 7 this invention. The absorbent corecomprises an absorbent layer 32 of fibrous material such as comminutedwood pulp fibers, cotton linters, rayon fibers, cotton staple, bleachedsulfite linters, other cellulosic or modified cellulosic fibers, and thelike. The absorbent core further comprises a body fluid-imperviouselement or barrier means 34 which overlies the bottom surface ofabsorbent layer 32. Barrier means 34 may comprise for example, a thinsheet of polyethylene or other suitable material. Where barrier means 34is not water dispersible, it is convenient that it be easily removedfrom the remainder of the diaper so as to minimize disposal problems.Fluid-pervious facing 36 overlies the top surface of absorbent layer 32.In the embodiment illustrated in FIGS. 4 and 5, it will be observed thatbarrier means 34 and fluid-pervious facing 36 are substantiallycoextensive and are joined together at their peripheries 38 by methodswell known in the art such bonding, ad-' hesive bonding stitching, andheat sealing techniques." While FIG. 4 illustrates a disposablediapr'fiati'ng'a particular construction, it will be recognized by thoseskilled in the art that the advantages accruing to the use of thenonwoven fabrics of this invention are equally applicable to disposablediapers having other, widely varying constructions. The absorbent coreis not limited to the structure illustrated, but may includeafluidpervious element, such as gauze, tissue, plastic netting and thelike, if it is desired to increase strength and/or structural integrity.

The nonwoven fabric of this invention is uniquely suited to serve as thefluid-pervious facing of a disposable diaper as shown in FIG. 4 becauseit is resistant to abrasion and exhibits acceptable tensile strengthwhen dampened or wetted with urine. Urine, as in the case of menstrualfluid, has a salt content of about 0.8 to about 1.5 percent by weight.As already indicated, the nonwoven fabrics herein are resistant tosolutions containing about 0.8 percent or more by weight of sodiumchloride. It will be apparent that by employing a waterdispersiblematerial for the barrier means and a waterdispersible, absorbent layer,the diaper of FIG. 4 can be safely and conveniently disposed of byflushing through a water closet. When the diaper of FIG. 4 has beenprovided with a barrier sheet that is not water dispersible, but has awater-dispersible, absorbent layer, then the layer and the facing may besafely flushed after they have been separated from the barrier means.

Those skilled in the art will readily understand that thewater-dispersible nonwoven fabric of this invention may beadvantageously employed in the preparation of a wide variety ofabsorbent products designed to be contacted with body fluids. Many suchabsorbent prod-' ucts need only comprise a core of absorbent material incombination with said nonwoven fabric. For example, an absorbentsurgical dressing could be made comprising a relatively thin,rectangular layer of absorbent material with the nonwoven fabricoverlying one or more sides thereof. Similarly, as in the case of atam-' Glacial Acetic Acid Sulfuric Acid (95% pure) The sodium sulfate isfirst added to a mixture of the acetic anhydride and acetic acid at roomtemperature, the sulfuric acid then being added at a rate such that thetemperature of the mixture does not exceed 544C.

The resulting solution is neutralized by adding small increments ofsodium sulfate and is then cooled to 4.4C. and filtered.

ETI-IOCEL Std., a trademark of the Dow Chemical Company forethylcellulose ether, is dissolved in acetic acid in a proportion of45.4 parts by weight of resin in 1 15 parts of acetic acid. ETHOCEL Std.has a degree of ethyl substitution of 2.46 to 2.58 and a 90 percent byweight solution of the resin dissolved in a mixture of toluene and ethylalcohol in the proportions of to 20 parts by weight, respectively, andmeasured at 25C., has a viscosity of 40 to 50 cps. The resin isdissolved in the acetic acid by mixing in a jacketed sigma blade mixer,for about 30 minutes at a jacket temperature of 38C. The jackettemperature is then dropped to 15C. and held at that temperature untilthe reaction mixture has cooled at 21C.

The sulfating solution is then added incrementally over a period of 20minutes, taking care not to exceed a reaction temperature of 32C. Theresulting reacted mixture is then added to an aqueous, ten percent byweight, sodium hydroxide solution in a ratio of one part by weight ofreacted mixture to ten parts by weight of the sodium hydroxide solution.This mixture is stirred vigorously and the pH is maintained atapproximately ten by the addition of requisite quantities of additionalten percent sodium hydroxide solution.

The resulting precipitated resin is separated from its mother liquor byfiltering in a Buchner funnel. The precipitate is then dried at atemperature of 50C. in a forced-air oven and ground in a Wiley mill, toa particle size of from one to two millimeters in diameter. The groundparticles are washed by combining them with ten times their weight ofboiling water and stirring vigorously while adjusting the pH to a valueof 5.5 with the addition of ten percent by weight of hydrochloric acidsolution. The precipitate resulting from this washing step is filtered,dried and ground in the manner described above. The washing step and thefiltering, drying, and grinding are repeated once again.

The resulting resin has a degree of sulfate substitution of 0.43.

EXAMPLE II With appropriate changes in the amount of sulfating agentemployed, the procedure of Example I was fol lqws Pr setsas t sspfs d qs ss 3,804,092 9 10 poration). Nonwoven fabrics were then prepared by Y,containing 7 percent solids. Nonwoven fabric D was saturating swatchesof the fibrous web with the above then made by using an engraved roll toprint bond a described binder solutions and drying at l50F for 90 sampleof the above mentioned fibrous web with binder minutes. The nonwovenfabrics so prepared comprised solution X and then drying the printed webover steam about 23 percent by weight of binder solids. 5 heated cansheld at about 270F. Nonwoven fabric E The nonwoven fabrics identified asA, B, C, respecwas prepared in the same way using binder solution Y.tively, were tested for tensile strength after immersion The patternengraved on the print roll comprised 6 in water, and after immersion inaqueous solutions conhorizontal wavy lines per inch, each engravingbeing taining, respectively, 0.9 percent and 1.6 percent 50- 0.024 inchwide and 0.010 inch in depth. The nondium chloride. woven fabrics soprepared comprised about 82 percent The following procedure was used forthe determinaby weight of viscose rayon and about 18 percent by tion oftensile strengths in tap water and in aqueous salt weight of resinbinder. solutions. The fabric to be tested was equilibrated for Thefabrics were tested, after equilibration for 24 24 hours at 72F. and 65percent relative humidity. hours at 72F and 65 percent relativehumidity, for ten- Fabric grain weight was determined in the usual way.sile strength, pinning strength, and flexural resistance. Three inch byone inch strips were cut from the fabric, Tensile strength wasdetermined by pulling 7 inch immersed in the desired test solution,removed, long by 3 inch wide samples on a Scott IP-IV incline drainedfor seconds, and gently blotted between plane tester having a jawspacing of 3 inches. Results paper toweling. The test strips were thentested on an of the tensile strength tests were reported in pounds perlnstron tester using a jaw spacing of 2 inches and a pull three inchwidth of fabric. speed of 2 inches per minute. Raw test data was con-Pinning strength was determined on a modified Scott verted to tensilestrength units of pounds per grain of lP-lV incline plane tester whereineach of the usual fabric (hereinafter, Lbs/Gm). jaws carried a safetypin for grasping the sample to be The results of the tensile strengthtests, which are set tested. Fabric strips measuring 7 inches by 3inches forth in Table ll, show generally that the tensile were used forthis test. The space between the safety strength of a given nonwovenfabric increases as the pins was 3 inches. Results of pinning strengthtests were salt content of the solution in which the fabric isimreported in pounds. mersed is increased. it is also noted that as thedegree Flexural resistance tests, which measure the softness of sulfatesubstitution in the cellulosic binder deof the nonwoven fabric, were runon a modified 3o creases, tensile strength after immersion ll'l waterre- Thwmg-Albert Handle-O-Meter. Test results are remains at the samegeneral level while tensile strength ported in arbitrary units--thehigher the number, the after immersion in each of the salt solutionsincreases. softer the fabric. 5

TABLE II Wet tensile, Wet tensile, Wet tensile, Resin, water 0.9% aq.NaCl 1.6% sq. NaGl Nondegree of woven substitu- Machine Cross MachineCross Machine Cross fabric tion direction direction direction directiondirection direction EXAMPLE III For purposes of comparison, a waterdispersible nonwoven fabric made according to the Example set forth Afibrous web was prepared from l /s inch, 1.5 dein Column 5 of U8. Pat.No. 3,554,788 was used as a nier, extra dull viscose rayon by a standardcarding control. Test results for the experimental fabrics andoperation. The web weighed about 280 grains per the control are given inTable III. The results show that square yard. Two sodium ethyl cellulosesulfate resins fabrics D and E, prepared with sodium ethyl cellulosewere prepared by the method of Example 1, except that sulfate havingdegrees of sulfate substitution of 0.19 different amounts of thesulfating agent were employed and 0.23, respectively, are suitable foruse as fluid perin order to vary the degree of sulfate substitution.The. vious facings in sanitary napkins having tabs.

TABLE III Dry tensile strength,

Fabric lbs/3 width Degree of weight, Pinning substitution, grains/Machine Cross strength, Flexural Fabric resin yd. direction directionpounds resistance 1 Us 3,544,788. *This test not run on control fabric.Experience has shown that a pinning strength of 2.5 is desirable wherethe nonwoven fabric is to be used as the fluid pervious facing lor acommercially acceptable tabbed sanitary napkin. resins had degrees ofsulfate substitution equal to 0.19 EXAMPLE IV and 0.23. The resin havinga degree of sulfate substitution equal to 0.19 was dissolved in 2: 1(weight) methanol/water mixture to give a binder solution, desig-Sanitary napltins were prepared using the construction of acommercially-available flushable napkin sold nated X, containing 1 1percent solids. The resin having by Personal Products Company, Milltown,New Jersey, a degree of sulfate substitution equal to 0.23 was disacorporation of the state of New Jersey, as MODESS solved in methanol togive a binder solution. designated (trademark of 1011115011 & Johnson)flushable feminine napkins. The construction of the MODESS flushablenapkin is generally similar to that illustrated in FIGS. 2 and 3. Thenonwoven fabrics of Example Ill, including the control fabric describedtherein, were used in place of the nonwoven fabric normally provided asthe covering material. Fifteen napkins were prepared for each of thefabrics to be tested. The sanitary napkins so made were then tested forflushability by flushing them through a testing system designed for suchpurposes. The testing system comprises an American Standard toiletfitted with 3 inch (I.D.) copper piping, approximately 1 l-l 2 feetlong. This pipe is connected to the toilet by way of an elbow and asuitable length of vertically placed piping. At the opposite end of thepipe, and at right angles thereto, there is placed an exit pipe about 20inches long. There is a tubular wire mesh screen, about 18 inches long,concentrically placed within the exit pipe, the screen carrying severalrows of barbs to simulate any internal rough surfaces in a sewagesystem. The test is conducted ly dropping the sanitary napkin into thetoilet bowl, waiting seconds, and then flushing. After each napkin isflushed, the screen is removed and the residue thereon is visually ratedby comparison with a set of standard photographs. A flus'hability ratingof excellent l good (2), fair (3), or poor (4) is then assigned to thenapkin under test.

runs for each of the test fabrics and the control. The napkins coveredwith the experimental fabrics were found to have better flushingcharacteristics than the napkin covered with the control fabric. Allnapkins were considered to be satisfactory for safe flushing through anaverage plumbing system.

TABLE IV Resin-Degree of Flushability Rating Fabric Substitution(Average of 15 runs) D 0.19 L9 (Good) E 0.23 3.0 (Fair) Control (None)3.5 (Fair-Poor) (U.S. Pat. No.

EXAMPLE V Fabrics D and E of Example III were tested for wet strength inthe presence of water and aqueous salt solutions of varyingconcentrations. A sample of the fabric to be tested was placed acrossthe mouth of a standard 400ml. beake rand items pTac eiwith aruesreafiaiAn area of the fabric approximately 2 inches in diameter was wetted withthe desired test solution and a 54 gram steel ballwas placed on thewetted area. The time in seconds required for the steel ball to breakthrough the test fabric was recorded. The test was repeated six timesfor each fabric and the results for each fabric were averaged. In someinstances testing was discontinued when a fabric under test did not failwithin a certain period of time. Test results which are summarized inTable V show that Fabric D (D8. 0. l9) and Fabric E (D5. 0.23) have verylow strength when wet with water. For a given degree of sulfatesubstitution, fabric wet strength increases as the sodium chlorideconcentration in the test solution is increased. At any givenconcentration of salt in the test solution, fabric wet strengthdecreases as the degree of sulfate substitution increases.

Swatches of fabrics D and E, when placed in water and even slightlyagitated, were observed to lose their integrity.

TABLE V Wet strength of fabrics, test results reported in secondsPercent N 9.01 in water 0 0.5 1.0 1.5 2.5 3.0 3.5 4.0 Fabric D 13.9 29.6 48. 9 86. 8 "600 *1, 600 *1, 800 Fabric E 6. 5 10. 3 18. 6 30. 5 228900 *1, 500 Control" U.S.

*Test stopped at this point without fabric failure. Typical values whenfabric of U.S. 3,544,788 is tested according to test outlined in ExampleV.

EXAMPLE Vl' a panel of 10 women. A quantity oFM ODES Sflushable sanitarynapkins, of the general type marketed by Personal Products Company ofMilltown, New Jersey, under the designation MODESS flushable femininenapkins, was prepared using Fabric D of Example Ill in place of thecover provided on the commercial napkin. Each member of the test panelwas provided with four such napkins for use during menstruation.

The average time of use was 4.75 hours; the average weight of fluiddeposited on a napkin was 7.58 grams, which is considered heavymenstrual flow. Of the forty returned products, 92.5 percent showedslight to no abrasion while the remaining 7.5 percent showed moderate toheavy abrasion. It was concluded from this test that Fabric D had verygood resistance to wet abrasion in the presence of menstrual fluid.

panel test showed that Fabric E had good to excellent abrasionresistance in the presence of menstrual fluid.

EXAMPLE Vlll A disposable diaper is made as follows: An absorbentfibrous layer, measuring about 11 inches by about 15 inches, is preparedfrom comminuted wood pulp. The absorbent layer, which weighs about 2025grams, is then placed on a piece of 1 mil polyethylenemrii measuringabout 12 inches by about 16 inches. This polyethylene film serves as abacking layer. A piece of nonwoven fabric D (Example III), alsomeasuring about l2 inches by 16 inches, is placed over the absorbentlayer in substantially coextensive relationship with the polyethylenefilm. This nonwoven fabric serves as the facing of the disposablediaper. Nonwoven fabric D and the polyethylene film are joined alongtheir peripheries with any suitable adhesive means, for example, anaqueous based polyvinyl acetate adhesive, so that the absorbent layer isconfined therebetween. Nonwoven fabric D has acceptable strength andgood abrasion resistance in the presence of urine. After use, nonwovenfabric D and the absorbent layer are separated from the polyethylenefilm. The nonwoven fabric and the absorbent layer are then easily andsafely disposed of by flushing in a toilet. It will be undersood thatthe above example is given for purposes of illustration only;

diaper comprises, in addition to the nonwoven fabric of this invention,a flushable absorbent layer and a flushable backing material, then theentire diaper may be dis?- posed of by flushing in a toilet.

What is claimed isz V 4 l. A water-dispersible nonwoven fabriccomprising: a layer of overlapping, intersecting fibers, said fibershaving a length not more than about two inches; and from about 4 toabout 35 percent by weight of the fabric of an alkali cellulose ethersulfate resin binder distributed in said fabric, said resin binderhaving an average of from about 0.1 to about 0.3 sulfate groups peranhydroglucose unit.

2. A water-dispersible nonwoven fabric according to claim 1, whereinsaid alkali cellulose ether sulfate resin has an average of from about0.15 to about 0.25 sulfate groups per anhydroglucose unit.

3. A water-dispersible nonwoven fabric according to claim 1, wherein thealkali cellulose ether sulfate resin is an alkali alkyl cellulosesulfate, said alkyl group having from one to four carbon atoms.

4. A water-dispersible nonwoven fabric according to claim 3, wherein thealkali alkyl cellulose sulfate resin is sodium ethyl cellulose sulfate.

5. A water-dispersible nonwoven fabric according to claim 3, wherein thealkali alkyl cellulose sulfate resin is sodium methyl cellulose sulfate.

6. A water-dispersible rionwoven fab ric accordi ng to claim 1, whereinthe alkali cellulose ether sulfate resin is an alkali hydroxyalkylcellulose sulfate, said hydroxyalkyl group having from one to fourcarbon atoms.

7. A water-dispersible nonwoven fabric according to claim 6 wherein thealkali hydroxyalkyl cellulose sulfate resin is sodium hydroxyethylcellulose sulfate.

8. A water-dispersible nonwoven fabric according to claim 6, wherein thealkali hydroxyalkyl cellulose sulfate resin is sodium hydroxypropylcellulose sulfate.

9. A water-dispersible nonwoven fabric according to claim 1, wherein thealkali cellulose ether sulfate resin is an alkali hydroxyalkyl alkylsulfate, said hydroxyalkyl and said alkyl groups each having from one tofour carbon atoms.

10. A water-dispers ible nonwoven fabric according to claim 9, whereinthe alkali hydroxyalkyl alkyl cellulose sulfate is sodium hydroxypropylmethyl cellulose sulfate.

11. A water-dispersible nonwoven fabric according to claim 1 wherein,said fibers are viscose rayon fibers.

12. A water-dispersible nonwoven fabric according to claim 1 wherein thelength of said fibers does not exceed about one and one half inches.

13. A water-dispersible nonwoven fabric according to claim 1, whereinsaid resin binder is distributed in said fabric in a predeterminedpattern.

14. A water-dispersible nonwoven fabric according to claim 1, whereinsaid fibers are viscose rayon fibers having a length of from about onehalf inch to about one and one half inches and said resin binder issodium ethyl cellulose sulfate.

15. A water-dispersible nonwoven fabric according to claim 1, whereinthere is from about 4 to about 20 percent of said resin binder by weightof the fabric.

16. A water-dispersible nonwoven fabric comprising: a layer ofoverlapping, intersecting textile fibers, said fibers being viscoserayon fibers from about one half inch to about one and one half inehe sin lengthtand from about 4 percentto about 20 percent of sodium ethylcellulose sulfate distributed in said fabric, said sodium ethylcellulose sulfate having an average of from about 0.15 to about 0.25sulfate groups per anhydroglucose unit.

17. An absorbent product for contacting body fluids comprising: anabsorbent core and a fluid-pervious, water-dispersible nonwoven fabriccovering at least a portion of said absorbent core; said nonwoven fabriccomprising a layer of overlapping, intersecting fibers, said fibershaving a length not more than about two inches; and, distributed in saidfabric, from about 4 to about 35 percent by weight of the fabric of analkali cellulose ether sulfate resin binder, said resin binder having anaverage of from about 0.1 to about 0.3 sulfate groups per anhydroglucoseunit.

18. An absorbent product according to claim 17 wherein said absorbentcore includes a fluid-pervious element.

19. An absorbent product according to claim 18, wherein thefluid-pervious element is tissue.

20. An absorbent product according to claim 18, wherein thefluid-pervious element is gauze.

21. An absorbent product according to claim 18, wherein thefluid-pervious element is a plastic netting.

' 22. An absorbent product according to claim 17, wherein said absorbentcore includes a fluidimpervious element.

23. An absorbent product according to claim 22, wherein thefluid-impervious element comprises polyethylene.

24. An absorbent product according to claim 17, wherein the absorbentcore includes a fl uid pervious element and a fluid-impervious element.

25. An absorbent product according to claim 24, wherein the fluidpervious element is tissue and the fluid-impervious material comprisespolyethylene.

2. A water-dispersible nonwoven fabric according to claim 1, whereinsaid alkali cellulose ether sulfate resin has an average of from about0.15 to about 0.25 sulfate groups per anhydroglucose unit.
 3. Awater-dispersible nonwoven fabric according to claim 1, wherein thealkali cellulose ether sulfate resin is an alkali alkyl cellulosesulfate, said alkyl group having from one to four carbon atoms.
 4. Awater-dispersible nonwoven fabric according to claim 3, wherein thealkali alkyl cellulose sulfate resin is sodium ethyl cellulose sulfate.5. A water-dispersible nonwoven fabric according to claim 3, wherein thealkali alkyl cellulose sulfate resin is sodium methyl cellulose sulfate.6. A water-dispersible nonwoven fabric according to claim 1, wherein thealkali cellulose ether sulfate resin is an alkali hydroxyalkyl cellulosesulfate, said hydroxyalkyl group having from one to four carbon atoms.7. A water-dispersible nonwoven fabric according to claim 6 wherein thealkali hydroxyalkyl cellulose sulfate resin is sodium hydroxyethylcellulose sulfate.
 8. A water-dispersible nonwoven fabric according toclaim 6, wherein the alkali hydroxyalkyl cellulose sulfate resin issodium hydroxypropyl cellulose sulfate.
 9. A water-dispersible nonwovenfabric according to claim 1, wherein the alkali cellulose ether sulfateresin is an alkali hydroxyalkyl alkyl sulfate, said hydroxyalkyl andsaid alkyl groups each having from one to four carbon atoms.
 10. Awater-dispersible nonwoven fabric according to claim 9, wherein thealkali hydroxyalkyl alkyl cellulose sulfate is sodium hydroxypropylmethyl cellulose sulfate.
 11. A water-dispersible nonwoven fabricaccording to claim 1 wherein, said fibers are viscose rayon fibers. 12.A water-dispersible nonwoven fabric according to claim 1 wherein thelength of said fibers does not exceed about one and one half inches. 13.A water-dispersible nonwoven fabric according to claim 1, wherein saidresin binder is distributed in said fabric in a predetermined pattern.14. A water-dispersible nonwoven fabric according to claim 1, whereinsaid fibers are viscose rayon fibers having a length of from about onehalf inch to about one and one half inches and said resin binder issodium ethyl cellulose sulfate.
 15. A water-dispersible nonwoven fabricaccording to claim 1, wherein there is from about 4 to about 20 percentof said resin binder by weight of the fabric.
 16. A water-dispersiblenonwoven fabric comprising: a layer of overlapping, intersecting textilefibers, said fibers being viscose rayon fibers from about one half inchto about one and one half inches in length; and from about 4 percent toabout 20 percent of sodium ethyl cellulose sulfate distributed in saidfabric, said sodium ethyl cEllulose sulfate having an average of fromabout 0.15 to about 0.25 sulfate groups per anhydroglucose unit.
 17. Anabsorbent product for contacting body fluids comprising: an absorbentcore and a fluid-pervious, water-dispersible nonwoven fabric covering atleast a portion of said absorbent core; said nonwoven fabric comprisinga layer of overlapping, intersecting fibers, said fibers having a lengthnot more than about two inches; and, distributed in said fabric, fromabout 4 to about 35 percent by weight of the fabric of an alkalicellulose ether sulfate resin binder, said resin binder having anaverage of from about 0.1 to about 0.3 sulfate groups per anhydroglucoseunit.
 18. An absorbent product according to claim 17 wherein saidabsorbent core includes a fluid-pervious element.
 19. An absorbentproduct according to claim 18, wherein the fluid-pervious element istissue.
 20. An absorbent product according to claim 18, wherein thefluid-pervious element is gauze.
 21. An absorbent product according toclaim 18, wherein the fluid-pervious element is a plastic netting. 22.An absorbent product according to claim 17, wherein said absorbent coreincludes a fluid-impervious element.
 23. An absorbent product accordingto claim 22, wherein the fluid-impervious element comprisespolyethylene.
 24. An absorbent product according to claim 17, whereinthe absorbent core includes a fluid-pervious element and afluid-impervious element.
 25. An absorbent product according to claim24, wherein the fluid pervious element is tissue and thefluid-impervious material comprises polyethylene.